Safety stop block



1957 s. w. ALSPAUGH 3,333,447

SAFETY STOP BLOCK Filed June 24, 1965 HM I! U l '|L Z6 i i i1 fi INVENTOR.

Ava ATTORNEY United States Patent 3,333,447 SAFETY STOP BLOCK Samuel W. Alspaugh, Tipp City, Ohio, assignor to General Motors Corporation, Detroit, Micln, a corporation of Delaware Filed June 24, 1965, Ser. No. 466,667 4 Claims. (CI. 72-31) This invention relates to mechanical presses of the type used for forming sheet metal and particularly to an arrangement for protecting such machines against excessive stresses in the operating parts thereof.

Mechanically operated presses for forming sheet metal or the like often include a stop block that is inserted between the movable ram of the punch press and a die supporting plate to prevent overtravel of a die punch carried by the ram. When misadjustment of the punch members reaches a certain point, this overtravel can be sufiicient to cause the driving components of the press to be undesirably stressed when the stop blocks limit the downward movement of the punch ram.

An object of the present invention, therefore, is to improve mechanically operated punch presses having a fixed member and a relatively movable member by the provision of a stop block assembly disposed between the fixed and movable punch press members including means operative to yieldably limit a predetermined overtravel of the movable member and additionally including means responsive to such overtravel for visually indicating such overtravel.

A further object of the present invention is to improve mechanically operated punch presses having a reciprocal member and a fixed member by the provision of a safety block assembly located between the relatively movable punch press members that includes means to initially indicate a proper height adjustment of the movable member of the punch press with respect to the fixed member, means for yielding limiting excessive movement of the movable member of the punch press with respect to the fixed member and means responsive to a predetermined overtravel of the movable punch press member to indicate such overtravel.

A further object of the present invention is to improve mechanically operated punch presses of the type including a movable member and a fixed member by the provision of a stop block assembly supported between the fixed and movable punch press members wherein the assembly includes a piston member normally positioned within a cylinder member by a deformable and extrudible support member filling a cavity having a predetermined volume and wherein the piston member is driven by a predetermined relative movement between the members of the punch press to force the extrudible support member outwardly of the fixed cavity to indicate overtravel of the movable member of the punch press.

A still further object of the present invention is to improve mechanically actuated punch presses having a fixed member and a movable member by the provision of a stop block assembly selectively engageable by the movable member upon a predetermined overtravel movement thereof, said stop block assembly including a piston member having a portion thereon directed into a cylinder member including a cavity of a predetermined volume, a mass of extrudible material filling said cavity, and means for communicating said cavity exteriorly of the block assembly whereby upon a predetermined overtravel movement of the movable member of the punch press, a

portion of the piston member is directed into the cylinder cavity to extrude material therefrom through the passageway for indicating overtravel of the movable member.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings wherein a preferred embodiment of the present invention is clearly shown.

In the drawings:

FIGURE 1 is a diagrammatic view of a mechanically operated punch that includes the stop block assembly of the present invention; and

FIGURE 2 is an enlarged vertical, sectional view of the present invention.

In FIGURE 1 of the drawings, a mechanically operated press is representatively shown that includes a press ram 12 reciprocated in a vertical direction by suitable drive means (not shown) such as a crank or eccentric mechanism and a suitable mechanical link for converting the movement of the crank or eccentric mechanism to reciprocation of the ram 12. Suitable hydraulic or pneumatic drives would be equally suited for association with the invention. On the underside of the ram 12 is secured a punch holder 14 having guide pin bushings 16, 18 thereon respectively slidably received over spaced apart, vertical guide pins 20, 22, each supported by a die shoe 24. The die shoe 24, in turn, is supported by a bolster plate 26 on a press bed 28.

In the illustrated arrangement the punch holder 14 has a punch member 30 secured thereto with a face 32 thereon that coacts with a complementary face 34 on a fixed die 36 supported by the die shoe 24. The complementary faces 32, 34 can take many forms but typically are designed to pierce or trim or form blank stock fed be tween the punch 30' and die 36 in a manner well know to those skilled in the art.

In order to carry out a desired press operation in the illustrated arrangement, the face 32 of the punch 30 preferably is located a predetermined distance from the face 34 on the fixed die 36 at the end of the downward stroke of the ram 12. The predetermined distance is established by adjusting the press ram 12 with respect to its drive mechanism through various adjutment arrangements depending on the type of punch press. Such an adjusted distance, however, is difficult to maintain in many punch press operations and in order to avoiddamaging the punch 30 and die 36 making up the die set, it is desirable to include the provision of a stop block be tween the movable punch holder and the fixed die shoe to maintain the predetermined desired spacing between the members of the die set at the end of the downward stroke of the ram.

In FIGURE 1, stop block assemblies'38, 40 are shown on either side of the die 36 supported by the die shoe 24 to be disposed between it and the movable punch holder 14. Each of the blocks'38, 40 cooperates with a depending member 42 on the punch holder 14 to limit ram travel to maintain a predetermined desired minimum spacing between the die and punch at the end of the downward stroke of the press.

The provision of stop blocks in the past has reduced the problem of die damage because of overtravel of the movable member of the die set. However, where the depth of travel of the ram becomes too deep because of operational misadjustment the limiting action of the stop blocks can produce severe damage to the crank shaft, crank eccentric or the like and means such as tie rods for operatively connecting the drive mechanism to the ram of the punch press.

To alleviate this problem, the present invention, as :best seen in FIGURE 2, each includes a cylindrical member 44 having a base 46 supportedon the die shoe 24. Within the member 44 is located a piston 48 having an upper flange 50 disposed at a predetermined height above the die shoe 24 at which point the downward travel of the press ram 12 is limited by engagement of the depending members 42 with the tops of the flanges 50.

the stop blocks 38, 40 of Within the base 46 of the cylindrical member 44 is located a cavity 52 which receives an extension 54 on the piston 48. The extension 54 is in engagement with a plug 56 that completely fills the cavity 52 below the extension 54. The plug 56 is of a deformable and extrudible composition such as aluminum, white metals, polycarbonates or any other suitable material having generally like structural characteristics. The portion of the cavity 52 that receives the plug 56 of extrudible material communicates with a transverse passageway 58 to a point exteriorly of the cylindrical member 44 and in the embodiment of FIGURE 2 has an indicator pin 60 disposed therein that is movable outwardly thereof upon the plug 56 being subjected to a predetermined pressure.

The piston 48 has a groove 62 formed therein into which is directed one end of a set screw 64 threaded through the wall of the cylindrical member 44 whereby the piston 48 is held against removal from the cylindrical member 44.

When the stop blocks 38, 40 are positioned between the die shoe 24 and press holder 14 or equivalent fixed and movable members of a mechanically operated punch press, in order to establish a predetermined spacing between the members of an associated die set such as the punch 30 and die piece 36, the punch is operated so that the press ram is at the bottom of its stroke and then the press ram is adjusted with respect to the drive mechanism of the punch press until the end of the depending members 42 are spaced immediately above the heads of the piston flanges 50 on the stop blocks 38, 40. With a selection of a stop block assembly having a predetermined vertical height and proper adjustment of the press ram, the relationship between the ends of the members 42 and their associated stop blocks serves to establish a proper spacing between the members of the die set.

In order to check the initial punch press adjustment the flange 50 is spaced above the upper end of the cylindrical member 44 by the plug 56 to form a space 66 therebetween in which a feeler gauge can be readily inserted to make sure that the piston 48 has not been driven downwardly by an undesirable overtravel of the press ram. Thus, the space 66 serves to indicate the slightest misadjustment of the ram that might cause an undesirable overtravel thereof with respect to the fixed portions of the punch press.

Another feature of the illustrated stop block assemblies 38, 40 is that they can be preset to immediately indicate an error in the selection of the depth of travel of the press ram 12 as might occur when an inexperienced operator is adjusting the machine for a particular operation. If an extreme error is made in such an adjustment, as soon as the machine is operated, the depending portions 42 on the punch holder 14 will engage the piston flanges 50 and following a predetermined pressure buildup will cause the extrudible plugs 56 to be squirted out the passageways 58 to either move pins 60 into a readily observable position or to direct a part of the plugs 56 exteriorly of the cylindrical members 46 so that the operator can know that the punch press has a depth of travel unsuited for the proposed die punching operation. The yield of the plug 56 will absorb a certain amount of the energy of the ram as it passes to too great a depth and will thereby serve to resiliently support the ram 12 in a manner to prevent excessive stresses being imposed on the die 36 by the punch 30 that would otherwise be produced by such overtravel. Additionally, since the stop block assemblies 38, 40 have a resilient give, depending upon the yield strength of the plugs 56 therein, the assemblies will tend to prevent excessive stress buildups in the drive mechanism of the punch press.

The extrudible plugs in the stop block assemblies 38, 40 thereby warn against misalignment due to errors in the original adjustment of the depth of stroke of the press ram and in cases where the feeler gauge space 66 is not continually checked and there is a buildup of operational misadjustment that can cause an undesirable overtravel of the press ram 12, the extrusion of the plugs can serves as a backup warning of such operational misadjustment.

While the embodiment of the present invention as herein disclosed constitutes a preferred form, it is to be understood that other forms might be adopted.

What is claimed is as follows:

1. A safety block assembly for association with punch presses having a die set including a fixed member and a movable member comprising, a first block member, a second block member slidably supported within said first block member, said block members forming an interior space therebetween, a mass of extrudible material in said space supporting a portion of one of said block members, said first and second block members being located by said mass for forming a feeler gauge space for indicating a proper setup between the fixed and movable members of an associated die set, one of said block members being movable with respect to the other of said block members upon a predetermined misalignment of the members of an associated die set to cause the supported portion of said one of said block members to press said mass, and port means in one of said block members for receiving a portion of the pressed mass for indicating the aforementioned misalignment.

2. In a mechanically operated die press, the combination of, a die set including a movable member and a fixed member, a stop block assembly operatively located between said fixed and movable members of said die set for limiting the relative travel therebetween, said assembly including first and second block members relatively movable with respect to one another, said block members having coactin-g portions forming a feeler gauge space for indicating a predetermined desired height relationship between said die set members, said block members forming a space interiorly of said assembly, a deformable plug located in said space, a portion of one of said block members being supportingly received by said deformable plug, a port in one of said block members communicating with said plug receiving space, said plug being deformed upon a predetermined relative movement of said block members to be extruded through said port for indicating misalignment of said die set members.

3. In a mechanically operated punch press, the combination of, a base support member, a movable ram, a die set having relatively movable die members, one of said die members being supported by said ram, the other of said die members being supported by said base support member, a stop block operatively disposed between said base support and said movable ram for limiting the relative movement therebetween, said stop block including a first member, a second member slidably received within said first member, said first and second block members forming an interiorly located space, a deformable plug located in said space for supportingly receiving a portion of one of said block members, said first and second block members having oppositely facing surfaces thereon, said surfaces being located by said deformable plug to form a feeler gauge opening for indicating a predetermined minimum spacing between said ram and said support base that corresponds to a desired setting of the die members, an opening directed through one of said block members for communicating the interior space therein with the exterior of said stop block, said first and second block members being relatively movable upon misalignment of said die set members to cause extrusion of said plug through said port to produce a visual indication of said misalignment.

4. In a mechanically operated punch press, the com bination of, a movable ram, a fixed support member, a first movement limiting member disposed on one of said punch press members, a second movement limiting member engageable by the other of said punch press memhers, said first and second movement limiting members being telescopingly arranged with one another and forming an interior space therein, said movement limiting members having oppositely facing surfaces thereon, a deformable plug located in said space for supporting a portion on one of said movement limiting members for 10- eating said surfaces in spaced relationship with one another to form a feeler gauge space to indicate a predetermined desired minimum spacing between said punch press members, an opening in one of said movement limiting members communicating said interior space exteriorly of said one of said members, said movement limiting members responding to a predetermined movement of the punch press members to extrude said plug through said opening to produce a visual indication of said movement,

said plug yieldably resisting a predetermined overtravel movement of said ram to prevent overstressing of the punch press.

References Cited UNITED STATES PATENTS 1,149,694 8/1915 Sonneborn 72465 2,396,814 3/1946 Besag 83-529 2,809,542 10/ 1957 Albers. 3,081,725 3/ 1963 Treer 7 2--26 3,192,751 7/ 1965 Baker 7235 CHARLES W. LANHAM, Primary Examiner. L. A. LARSON, Assistant Examiner. 

1. A SAFETY BLOCK ASSEMBLY FOR ASSOCIATION WITH PUNCH PRESSES HAVING A DIE SET INCLUDING A FIXED MEMBER AND A MOVABLE MEMBER COMPRISING, A FIRST BLOCK MEMBER, A SECOND BLOCK MEMBER SLIDABLY SUPPORTED WITHIN SAID FIRST BLOCK MEMBER, SAID BLOCK MEMBERS FORMING AN INTERIOR SPACE THEREBETWEEN, A MASS OF EXTRUDIBLE MATERIAL IN SAID SPACE SUPPORTING A PORTION OF ONE OF SAID BLOCK MEMBERS, SAID FIRST AND SECOND BLOCK MEMBER BEING LOCATED BY SAID MASS FOR FORMING A FEELER GAUGE SPACE FOR INDICATING A PROPER SETUP BETWEEN THE FIXED AND MOVABLE MEMBERS OF AN ASSOCIATED DIE SET, ONE OF SAID BLOCK MEMBERS BEING MOVABLE WITH RESPECT TO THE OTHER OF SAID BLOCK MEM- 